Remote meter reading system for kwh watthour meters and demand meters

ABSTRACT

A remote meter reading system for providing automatic readout by interrogation equipment located remotely from the meters having the capability of providing demand meter reading including the KWH reading and the demand meter reading for billing purposes regardless of the time of readout of the demand meter reading. Word generator generates words for transmission by an associated transponder in response to an interrogation signal from the remote source.

United States Patent 1191 Bruner et al.

1451 July 17, 1973 REMOTE METER READING SYSTEM FOR KWH WATTHOUR METERSAND DEMAND METERS Inventors: James N. Bruner; Dan McAulift,

both of Springfield, lll.

Assignee: Sangamo Electric Company,

Springfield, lll.

Filed: Nov. 4, 1971 Appl. No.: 195,695

US. Cl 340/151, 235/l5l.31, 324/103 Int. Cl. G0lr 11/64 Field of Search324/116, 103;

References Cited UNITED STATES PATENTS 3/1970 Baggott 324/103 DENIM3,258,692 6/1966 Jacomini et al 340/l5l Primary Examiner-John W.Caldwell Assistant Examiner-Robert J. Mooney Attorney-John A. Dienner,Arthur J. Wagner et al.

[57] ABSTRACT A remote meter reading system for providing automaticreadout by interrogation equipment located remotely from the metershaving the capability of providing demand meter reading including theKWl-l reading and the demand meter reading for billing purposesregardless of the time of readout of the demand meter reading. Wordgenerator generates words for transmission by an associated transponderin response to an interrogation signal from the remote source.

24 Claims, 9 Drawing Figures REA DING 5MHUTE HULTIPLEXE mimic-mu 3.147.068

' SHEET a 0F 7 COMPARATOR AND STORAGE CKZ' 29 STORAGE 394 CKT. 340

INVENTORS. JAMES N. BRUNEI? BY DAN M AUL/FF yawn MM/44.

A TTYS.

PAIENIEUJUL 1 1 M 3.147. use

SHET 5 0F 7 3/ 39 (H53) STURE ALTERNATE MONTH STORAGE 5K7 500 35 fill M3 492 493 ALT MONTH ACCUMULATOR lNVE/WOR JAMES N. BRUNEI? 0411/ M N/LIFF1 REMOTE METER READING SYSTEM FOR KWH WATTHOUR METERS AND DEMAND METERSBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to remote meter reading systems, and more particularly to aremote meter reading system in which KWI-l meters and demand meters maybe read from a remote station.

2. Description of the Prior Art While the utility companies at presentgenerally utilize meter reader personnel for reading the meterinformation which is provided by the utility meters (i.e., gas,electricity, water and the like), significant strides have been made inrecent years in the development of fully automatic meter readingsystems. Generally speaking, most remote reading systems basicallycomprise an encoder device which is attached to the existing meter tosense the meter reading, storage means for storing the sensed reading,and transponder means for selectively transmitting such information overan associated communication link to a central station in response to aninterrogation signal from such station. The modes and links used intransferring the information from the individual meters to the centralpoint will vary with the system. In one novel system which is set forthin the copending application, which was filed July 10, 1970, andassigned Ser. No. 53,745, a mobile van unit travels over a predeterminedroute in a community, and in its travel transmits interrogate signals tothe meter equipment at the houses located along such route of travel.The remote meter reading equipment at each house, in response to theinterrogating signals, transmits a word which includes an identificationnumber for the meter being interogated and the present reading of suchmeter. A van receiver means routes the incoming words to van carriedstorage means for subsequent use in the preparation of the customersbill.

Other types of systems which have been developed include arrangements inwhich the telephone line of the subscriber is used as a link with thecentral station, arrangements in which radio transmitters are attachedto the meter to provide wireless transmission of the information to acentral point, and arrangements in which the power lines of thesubscriber are used as the link between the individual meters and thecentral station.

While different types of systems are being developed, in each instancethe known systems have included transponder equipment which has meansfor sensing the quantity of the commodity used and means for providing apulse output indicating the amount of commodity used by the customer. Inthe case ofa transponder used on electrical meters, for example, mostsystems use a sensor which detects the number of revolutions of themeter disc, and a pulse generator which provides pulses to indicate thenumber of such revolutions, and thereby the electricity which has beenused by such customer. Such reading as obtained by the remote meterreading system or by a meter reader is known in the field as KWI-Ireading.

In a number of locations, the utility finds it necessary to charge thecustomer at a rate which is determined by the maximum amount ofelectricity which is used in a given period. In such instances, a meter,conventionally designated as a demandmeter, is employed to provide thekilowatt hour (KWH) reading for a given billing period along with themaximum demand which has occurred during a given interval in the samebilling period. A demand meter will therefore include, in addition tothe conventional register which indicates the kilowatt hours used, apointer which is advanced along an indicating scale to indicate themaximum reading for each time period in a billing period 15 minuteintervals are frequently used as the periods for measuring demandconsumption). If the amount of electricity used for a 15 minute periodis less than the maximum amount used in a previous period, the indicatorwill not be moved from its earlier position, and the pusher member forthe pointer will be restored to zero position to reinitiate measurementof the electricity used in the further period. However, if the amount ofelectricity used in such 15 minute period is greater than the amountused in any previous 15 minute period, the pusher member will haveadvanced the pointer to a position which identifies the larger readingand thereafter will be reset to measure a further 15 minute interval.

As presently used, when the meter reader makes his periodic reading ofthe kilowatt hour reading and the demand reading, the demand meterpointer must be reset to zero so that the measurements for the nextbilling period may be initiated.

The remote meter reading systems developed to date have apparently beenlimited to the readout of kilowatt hour readings, and as a result have asomewhat limited application. That is, without the capability of alsoreading demand meters (which in addition to providing different typereading must also be periodically reset) special meter readers must besent out to the various locations in the system for the sole purpose ofreading the demand meters. The utility of the automatic reading systemsdeveloped heretofore is therefore of limited scope, and such systemshave provided only a partial solution to the remote meter readingproblem.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a system which effects the novel reliable and efficient remotereadout of electrical demand meters.

It is a further object of the present invention to provide a system ofthe type in which a single meter sensor may be used to provide theinformation for the normal kilowatt hour reading and the demand meterreading.

To this end the novel system includes a pulse source which providespulses which indicate the amount of electricity being consumed to anassociate counter, whereby the total count at any given Jime can beautomatically provided in response to an interrogation signal. It willbe apparent that subtracting of the previous count from the currenttotal count will provide an indication of the amount of power (i.e., aKWI-I reading) used during the intervening interval. The system furthercomprises a 15 minute demand counter circuit which is connected to thesame pulse source to count the number of pulses which occur in each 15minute interval. Such pulses are fed to a comparator and storage circuitwhich is enabled at the end of each 15 minute interval to compare thecount stored therein with the count which occurred during a previous 15minute interval. If the new count is less than the stored count nochange is made in the stored count, and the 15 minute demand counter isreset. If the new 15 minute placed in storage.

A further timer means measures approximately a 30.4 day (730.5 hours)period and at such time an output signal is provided to control acomparator in the storage circuit to transfer the stored count (i.e.,the maximum demand count for the previous month) to one of twoaccumulators. After such transfer, the storage circuit is reset and thenext count for the subsequent 30.4 day period is stored in the secondaccumulator. As will be shown, the time of readout of the meters in autility system may vary significantly over a years period, and it isnecessary that the output reading of the demand meter be accurateregardless of the times of such readings.

The counts in the two accumulators and the count in the comparator andstorage circuit (three separate counts identified as counts B,C,D) arecontinually made available along with the storage KWI-I count toassociated word generator circuitry. As will be shown such circuitcontinually generates and supplies words to an associated transponderfor transmission to the remote source in response to receipt of aninterrogation signal therefrom.

The word generator source includes a first multiplexer which isconnected to provide a series of meter address bits which identify themeter address of the demand meter and a series of identification bitswhich identify the source of the count information which was included inthe word (i.e., the source of counts B, C, D or the KWH count). A secondmultiplexer means is operative to provide the information bits for eachword which represents the value of the counts B, C, D or KWH. Forreliability in the present system each word is transmitted five times.In one cycle of the system, therefore, twenty words are generated, theinformation bits in one set of five words representing the count in thecomparator and storage circuit, the information bits in a second set offive words representing the count in one accumulator, the informationbits in a third set of five words representing the count in the secondaccumulator, and the information bits in a fourth set of five wordsrepresenting the KWH counts stored in the KWl-l meter.

The system cycles in a continuous manner, continuing to provide such setof words to its associated transponder. The transponder in turn providessuch information to the mobile van unit in response to interrogatingsignals which are received from such unit. The van unit stores suchinformation for processing by associated processing equipment on the vanor for use by data processing equipment located in the central station.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a block diagram of the novelsystem including the circuitry which is used in the generation of wordsindicating the information provided by the demand meter for use inreadout by remotely located interrogating apparatus;

FIG. 2 is a schematic circuit showing of the time base generator whichis used to provide the timing signals to the word generation circuitryin the system;

FIG. 3 is a schematic circuit showing of the system demand clockgenerator and the demand counter;

FIG. 4 is a schematic showing of the comparator and storage circuitwhich stores the maximum count obtained in any minute interval of each30.4 day period;

FIG. 5 is a schematic circuit showing of the accumulators whichaccumulate the maximum counts of demand meter readings for alternate30.4 day periods;

FIG. 6 is a schematic circuit showing of the meter ad dress multiplexer,the 15 minute demand multiplexer, the alternate month accumulatormultiplexers, and the KWH multiplexer which are used to provide theinformation included in the words generated by the system;

FIG. 7 is a schematic circuit showing of the multiplexer which isutilized to select the information output from the differentmultiplexers of FIG. 6 for application to the system transponder;

FIG. 8 is a time diagram of the data time slots and start pulse timeslots used in the signalling pattern of the systems; and

FIG. 9 is a showing of an alternate transponder for use with the system.

GENERAL DESCRIPTION With reference to FIG. ll, there is set forththereat a block diagram of the novel system which is adapted for use inthe automatic readout of demand meters, and particularly of demandmeters which are used in the novel remote meter reading system set forthin the above identified copending application. As will be shown, a pulseencoder of the type shown in such application continually providespulses representing the power measured by the demand meter DM over aninput circuit 27 to a demand counter 26 which accumulates a count ofsuch pulses for a measured period. The novel system of FIG. 1 utilizessuch information to provide demand reading information to an associatedremote meter reading installation.

More specifically with reference to FIG. 1, the system basicallycomprises a time base generator 10 which generates and provides timingpulses over conductors 12-18 at given time periods in a cyclic patternto each of a number of circuits in the system in a manner to be setforth.

A first pulse output is fed over conductor 12 at a 3 .24 Hz frequency toa demand clock generator 20 which is controlled by such pulses (a) tomeasure fifteen minute intervals, and (b) to provide an output pulseafter each fifteen minute interval over conductor 21 to a comparator andstorage circuit 29. With receipt of such pulses at the end of eachfifteen minute interval, comparator and storage circuit 29 via path 28looks at the pulse count accumulated in the demand counter 26, and ifthe count accumulated by demand counter 26 in the previous fifteenminute period is larger than the count of any previous fifteen minuteinterval stored in comparator and demand storage circuit 29, the newlarger count will be automatically stored in circuit 29.

In addition to the 15 minute interval clocking pulse to effect suchevaluation of the demand reading for each fifteen minute interval,demand clock generator 20 also provides a 15 minute delay (or clear)pulse over conductor 22 which is delayed with respect to the clockingpulse on conductor 21 by l,us. The lus delay permits the comparatorstorage circuit 29 to make the evaluation described, and as the clearpulse is applied to conductor 22, demand counter 26 is reset to therebyinitiate a new count which represents the demand for the next fifteenminute interval.

At the end of each 730.5 hours (approximately 30.4 days) demand clockgenerator 20 is also operative to provide a transfer pulse alternatelyover paths 23, 24.

Since the comparator and demand storage circuit 29 continually checksthe count for each minute period with the highest previous count, (andmakes a change only if a higher 15 minute count has occurred) the countstored in such circuit at the end of 730.5 hours (30.4 days) willclearly represent the largest customer demand in any 15 minute intervalfor such period. With the receipt of each such transfer pulse, themaximum demand count for the previous 30.4 days which is stored incomparator and storage circuit 29 will be transferred to one of the twomonthly accumulator circuits 34 or 38 dependent upon which accumulatorhas been enabled by the transfer pulse via alternate paths A briefinterval after such monthly transfer, a pulse (referred to hereinafteras a monthly clear pulse) is fed by demand clock generator overconductor to clear the information in comparator and storage circuit 29and thereby reset such circuit to determine and store the maximum 15minute interval count which occurs in the next 30.4 days.

In addition to storing and determining the maximum demand information inthe manner described above, the novel system is also operative toprovide a readout of the total KWH used by the customer and registeredon the demand meter DM. More specifically, the input pulses fed overpath 27 to demand counter 26 by the demand meter DM are also fed overconductor 43 to a meter scale divider 44 and path 45 to a KWl-l counter46. As a result, the total pulse count output from the demand meter DM(which represents total energy measured by the meter from the time ofinstallation of the meter) is thus continually registered on KWH counter46.

The demand meter information which is stored in the storage circuits 29,34, 38, and 46 in such manner as cyclically gated out to an associatedtransponder unit 58 (which may be of the type shown in my copendingapplication or the novel transponder set forth hereinafter) under thecontrol of the time base generator 10.

Digres sing briefly, it will be recalled that in my previous system eachtransmitted word comprises a start pulse and 29 information bits, the 29information bits being separated by reference signals (logic 1 signals)to provide extremely reliable information readout by the remote unit. Tofurther insure reliable signal readout, each word generated istransmitted five times to the remote interrogating source. The manner ofgeneration of words for use in transmitting the accumulated demand meterinformation in-such system is now briefly described.

With reference once more to FIG. 1 time base generator 10 which includesa 3.840683 megahertz crystal generator (i.e., a frequency output relatedto that of the system shown in my copending application) provides thereference 1" signal output over path 13 at the 1875.33 Hz rate forinterspersing with the information bits in each word which representsthe accumulated demand meter information. The start pulse for each wordis provided over path 14 by time base generator 10 at a frequency rateof 32.4 Hz and in turn over OR gate 53 and path 54 to the transponder58.

The word bits representing the meter address and accumulated demandmeter information is fed to the same transponder 58 by a group ofmultiplexers 32, 36, 40, 48, 50 and 52. For such purpose, time basegenerator 10 further provides a 1 of 16" select pulse over fourconductor path 15 to (a) meter address multiplexer 52, (b) 15 minutedemand multiplexer 32, (c)

' alternate month demand accumulator multiplexer 36,

(d) alternate month fifteen minute demand accumulator multiplexer 40,and (e) the KWl-l counter multiplexer 48.

That is, after the start pulse (three logic 1 levels followed by a logic0 level) is placed on path 14 by time base generator 10 (in time slot 29ofa word), time base generator 10 places the first pulse (0001) on 1 of16" four conductor path 15 to multiplexers 52, 32, 36, 40, 48.Simultaneously multiplexer 52 will be enabled by a signal on path 17from time base generator 10. Since multiplexer 52 has its fourteen mostsignificant inputs hardwired with the address preassigned to the demandmeter DM, multiplexer 52 will cause such fourteen bits in the meteraddress to be fed sequentially over path 44 and OR gate 53 to thetransponder 58 as the first fourteen input selection signals aresuccessively applied to path 15 by time base generator 10. The 15th and16th bits output by multiplexer 52 will be determined by the signals onthe 1 of 4 meter-select two conductor path 16 (00in the first instance).As will be shown, the same l to 4 signals are fed to meter readingmultiplexer 50 which in turn selects the output of a corresponding oneof the multiplexers 32, 36, 40 and 48. Since the same bits are used asthe 15th and 16th bits in a word following the first 14 address bits, itis apparent that such bits identify the source of the word information(i.e., 00 will represent multiplexer 32; 01 will represent multiplexer36; 10 will represent multiplexer 40; and 1 1 will represent multiplexer48).

As noted above, the 1 of 16 signals output from time base generator 10over path 15 to multiplexer 52 are simultaneously fed to multiplexers32, 36, 40, 48, and such multiplexers will be continually cycled(simultaneously with multiplexer 52) to place the information appearingon their respective inputs over their associated output paths 33, 37,41, 49 to multiplexer 50. However, such information transfer is withouteffect during the period the meter address portion of the word isprovided by multiplexer 52 since during such period multiplexer 50 isdisabled.

After the start pulse on path 13 followed by the sixteen bits have beenoutput from the multiplexer 52, time base generator 10 provides anenable signal on path 18 to thereby enable multiplexer 50 (andsimultaneously removes the enable signal from path 17 to disablemultiplexer 52). Since the code on 1 of 16" path 15 is 0001 multiplexer50 will be enabled to extend the input on the first input path 33 from15-minute demand multiplexer 32 over path 51 to OR gate 53 and over path54 to transponder 58. The output signals provided by time base generator10 result in the cyclic transmission of such information (the 14 bitmeter address, the two identification bits which identify theinformation as output from the lS-minute demand multiplexer path 51, the12 bit meter information provided by multiplexer 32 and the start pulse)five successive times. The five repeated transmissions are accomplishedby reason of the fact that the 1 of 4 coded select signals on path 16are not changed by time base generator 10 until each word has beengenerated five successive times.

After the fifth generation and transmission of such word, the 1 of 4select signal output on path 16 from time base generator 10 changes from00 to 01. The time base generator 10, in the manner of previous cycles,once more enables the meter address multiplexer 52 via path 17 andthereafter enables multiplexer t) via path 18. Since the select signalon path to is 01, the multiplexer 50 will now select the bit informationoutput from alternate path multiplexer 36 and input over conductor 37 tomultiplexer 50. The word including the meter address, code 01 (toidentify the information as output from multiplexer 36) the informationfrom multiplexer 36 and the start pulse is output five successive times,and the time base generator 10 thereupon changes the signal on path 16to l0. Multiplexers 52 and 50 are thereupon enabled to generate a wordwhich includes the meter address, the identification code 10 formultiplexer 40, the information provided by multiplexer 40 and the startpulse, which word is generated five successive times. After the fifthgeneration, time base generator 10 changes the signal on path 16 to ll,and multiplexers 52, 50 provide a word including the meter address,identification code ill for multiplexer 48, the information provided bymultiplexer 48 and the start pulse. Again such word is generated fivetimes. The system cyclically generates each of the four different wordsin such manner, and transmits the same to the transponder 58.

The information output by multiplexers 32, 36 and 40 is read out byassociated interrogation equipment in the manner described in detail inthe copending application. In one preferred embodiment, such equipmentis included on a moving van which transmits interrogate signals to thesystem associated with the meter words in the system. The informationobtained by the receiver equipment on the van is fed to memory equipmentfor use in calculating the maximum demand reading in a novel manner nowset forth.

Briefly stated, the van equipment (which may be of the type shown in thecopending application) may include storage means operative to store thefour output words received from the transponder 58 which words includethe information provided by multiplexers 32, 36, 40 and 48. Theinformation output for each meter, as thus stored, is compared with theinformation previously obtained from the same source.

The data processing equipment then determines the change, if any, in theinformation obtained from the Rule 1: lf the reading output from neitheraccumulator 34 nor 38 has changed, the reading in storage circuit 29 isused as the maximum KW demand.

Rule 2: If the reading of either accumulator 34 or 38 has changed, butnot both, the change is used as the maximum KW demand.

Rule 3: lfthe reading provided by both accumulators 34, 38 has changed,the larger change is used as the maximum KW demand provided less than60.9 days have elapsed since the previous interrogation.

Rule 4: In the unlikely event that more than 60.9 days have elapsed, avalid demand reading can still be obtained provided less than 91.3 dayshave elapsed. The readings of both accumulators 34 and 38 will havechanged at least once, but one of them may have changed possibly morethan once. In such event either the smaller change is used for maximumKW demand, or the reading on storage circuit 29 is used if such readinghappens to be greater.

In a typical example (and for purposes of simlicity assuming a newinstallation), if a maximum demand of 120 KW is obtained in the first30.4 days, it will be seen that storage circuit 29 will have a pulsecount which represents 120 KW, and accumulator 34, 38 will still readzero.

Assuming 8O KW was the maximum demand used during the next 30.4 dayperiod, the pulse count on storage circuit 29 will represent 80 KW, andthe pulse count on accumulator 34 will represent 120 KW. Accumulator 38will still read zero.

Assuming that a further 30.4 day period now occurs and that the maximumdemand is 90 KW, the readings on storage circuit 29 will be 90 KW; thereadings on accumulator 34 will be 120 KW (i.e., such readinginformation changes every second month) and the reading on accumulator38 will be 80 KW. It will be seen that the reading on accumulator 38 haschanged, but the reading on accumulator 34 has not changed.

Assuming now that the fourth period of 30.4 days has occurred, and thatthe reading on storage circuit 29 for the fourth period is 30 KW, thereadings on the accumulators 34 and 38 will be 210 KW and 80 KWrespectively. The manner in which demand readings are provided will beapparent from the following table:

previous interrogation. The kilowatt-hour consumption is determined bythe change in the output of multiplexer 48, and the maximum KW demand isdetermined by an analysis of readings provided by multiplexcrs 32, 36,and 40.

It will be seen from such table that if the meter DM has beeninterrogated in less than 30.4 days (Time T1) or between 30.4 and 60.9days (Time T2), and using Rules 1 and 2 set forth above, the correctreading in each case would have been 120 KW. Although unlikely, if thefirst interrogation had been made between 60.9 days and 91.3 days (TimeT3), the probable reading of 90 KW on storage circuit 29 would have beenused, (Rule 4); i.e., 90 KW, the reading on storage circuit 29, islarger than KW, which is the smaller change on accumulator 34 or 38). Ifthe actual demand between 60.9 days and 91.3 days had not reached 90 KW,then 80 KW would have been used as the demand reading.

As another example, if the first interrogation was made at T2 and asecond interrogation at T4, the second months demand reading would berecorded as 90 KW (the larger changeRule 3). If the second monthsinterrogation had been at T instead of T4, the demand reading would alsobe 90 KW (the smaller changeRule 4).

It is apparent that the values of the KW demand readings can varydepending upon the time which elapses between interrogations, but thisis also true of present manual reset methods on conventional demandmeters. Since most loads tend to be repetitive from month to month, theactual time of manual reset or for interrogation by the presentequipment is not considered to be critical.

Time Base Generator With reference now to FIG. 2, there is shown thereata time base generator which may be utilized to pro vide the desiredsynchronization of operation of the various components of the system. Asthere shown, a crystal oscillator 201 is operative to provide a 1.920341megahertz output over path 202 to 16 di vider 203 which in turn providesan output over path 204 of 120.221 KHz to 16 divider 205 which at itsoutput provides a 7501.3 I-Iz signal over path 206 to 4 divider 207.Chips 201, 203, 205, 207 may respectively comprise one-half SN74LO0N,SN74L93N, SN74L93N and SN74L73N which are currently available from TexasInstruments Company, Dallas, Tex. The output of divider 207 is providedover outputs 208, 209, 210, 211 respectively as now described in moredetail.

More specifically, output path 210 (C) comprises a 1875.33 Hz outputover path 210 to a further 16 divider 212 which has one of its outputsconnected over path 218 to 10 divider 219, and 10 divider 219 has itsoutput connected over path 224 to 4 divider 225.

Divider 212 has four additional outputs 213-216 which provide the pulseson the 1 of 16 select path 15, as will be shown. Divider 219 has its 2output 220 connected back to the input of the 5 section to provide a 10function over path 224 to 4 divider 225. The BC outputs of divider 207,the PG outputs of divider 212 and the H output of divider 219 areconnected to gate 232 to provide the start signal over path 14. theoutputs of divider 225 are connected to provide the l of 4 select signalover paths 16, 16'. The 2 output of divider 219 is also connected overpath 17 and via inverter 239 to output path 18 as will now be more fullyset forth.

In more detail, it will be recalled that each word comprises 29 timeslots. Time slots 1-28 have a sync signal (reference 1) and a data bitand time slot 29 has a start pulse comprised of two logic 1 signals anda logic 0 signal. The information bits for the first 16 time slotscomprise a meter address of 14 bits plus 2 code bits indicating thesource of the demand meter information and 12 bits of demand meterinformation (the information bits being separated by reference 1 bits)or a total of 28 in formation bits. In order to establish a 29 bitpattern for the system, a decode gate 240 (FIG. 2) has its inputconnected to the outputs DFG of divider 212 and 2 output of divider 219.As a result with the count of 29 pulses of the 1875.33 Hz input, each ofthe inputs to gate 240 will be logic 1 and gate 240 will provide asignal output to enable the associated circuitry to provide a resetpulse over path 249 to divider 212 whereby a further count of 29 pulsesis initiated.

More specifically, the output of AND gate 240 is connected over path 241to a one shot multivibrator 250 which provides an elongated pulse toinsure proper clearing of the divider 212. Normally, the output of NANDgate 240 is logic 1. As the output goes to 0 logic (i.e., each time acount of 29 is recorded by divider 212, 219) the output of NAND gate 242goes to logic 1, the input to inverter 247 becomes logic 1, and theoutput of inverter 247 becomes logic 0. Such output over path 243 to thesecond input of NAND gate 242 locks gate 242 until capacitor 245discharges over resistance 246. In one embodiment the values of RC 245,246 were chosen to provide a lus pulse output, it being apparent thatthe value of such R and C can be selected to provide pulses of differentlengths. The lus pulse provided in this example is fed over inverter 248and path 249 to the reset input of divider 212 to start-a subsequentcount of 29 pulses.

As noted above, time base generator 10 provides further time pulses tothe system via paths 12-18 which are synchronized with and related tothe 29 bit word framework described above.

It will be initially recalled that in the system of the copendingapplication, sync pulses (reference one pulses) are generated betweeneach data bit output from the transponder 58. Such pulses are derived inthe time base generator 10 by NAND gate 228 which has its in putsconnected over conductors 209, 211 to the D, C output of divider 207 toprovide sync pulses at the 7501.3Hz rate over path 13 to the OR gate 53and transponder 58 (FIG. 1). Since such pulses occur in the sync portionof each time slot of each word no further description appears necessary.It will be apparent that divider 207 corresponds to the pulse divider241 shown in the copending application and that each four counts thereofdefine a time slot for use with the system of such disclosure.

The time base generator 10 further puts out a start pulse at a frequencyof 32.4 Hz (whereby each new word output from the system occurs at afrequency rate of 32.4 Hz) i.e., the time required to generate each wordin the system. The start pulse on conductor 14 is generated by NAND gate231 which has three inputs connected over conductors 215, 216, 220 tooutputs F, G, H of dividers 212, 219, whereby such inputs will go tologic 1 each time a count of 29 is output by dividers 212, 219 (i.e., asshown in FIG. 8, the 29th time slot of the system comprises two logic 1intervals followed by a logic 0 interval). Gate 232 has a further inputconnected to the output of NAND gate 231 which has its inputs connectedto the B, C, outputs of divider 207. As a result the start pulse willoccur at time slot 29 and will comprise a sync pulse followed by a logic0 pulse. The time slots for the stored pulse, sync pulse and data pulsewhich make up each word are described more fully in the copendingapplication.

The DEFG outputs of divider 212 are connected over conductors 213-216 inpath 15 and provide a changing signal (I of 16 code) for each time slot(i.e., 0000, 0001, etc.). As will be shown the coded signals on path 15are fed to multiplexers 32, 36, 40, 48 and 52 for use in gating theaccumulated data information into the data bit interval of an unexpiredtime slot in each word.

The 2 output of divider 219 over conductor 220 to paths 17 and 18determines the bit information to be provided in each word. Thus thesignal on conductor 220 (path 17) will be logic 1 during the first 16counts from dividers 212 and the meter address to the transponder 58. Asthe count of divider 212 continues, the output of divider 219 willchange to logic and such signal over conductor 220 and inverter 239 willresult in logic 1 on' path 18 which enables multiplexer 50 to providethe bit information to be transmitted for the next 12 time slots (itbeing recalled that reset occurs at count 29).

The source of the bit information provided for the 12 time slots isdetermined by the signals on the l-of-4 conductors 16,16.

It will be recalled that divider 219 is comprised of a 2 and 5 counter.Thus an output is provided by divider 219 to divider 225 only after eachword has been generated five times by the signals on conductors 15, 17,18. After five signals over conductors 17', 18, respectively, the pulseon path 224 from divider 219 causes the output of divider 225 to advanceone count and provide a different select signal over its L,IVI,I, I],outputs and the two conductor paths 16, 16' respectively(i.e.,00, 10,0l,11 on path 16 and 11, 01, I0, 00 on path 16'). Such signals as appliedvia path 16' to multiplexer $0 (FIG. 1) enables such multiplexer tosuccessively select the bit output from multiplexers 32, 36, 40, 48 forinclusion in the last 12 bits of each word, a different selection beingmade after each five word transmission by reason of the changing code onpath 16'. The signals on path 16 as fed to multiplexer 52 (FIG. 1) aswill be shown identify the one of the sources (32, 36, 40, 48) fromwhich the information is being obtained, such code being placed in the15th and 16th bits of the 16 bit information provided in each word bymultiplexer 50.

In addition to providing the timing signals for the word generatordescribed above, the time base generator also provides timing signalswhich are used to determine the minute intervals of the system operation. That is, the output of divider 225 which occurs at a frequency of375/116 Hz is fed over path 12 to a demand clock generator 20 (FIGS. 1,3) to control the same to transfer the counts accumulated in demandcounter 216 in each 15 minute interval to the comparator and demandstorage circuit 29.

Demand Clock Generator 20 As explained earlier, demand clock generator20 (FIG. 1) provides a pulse each fifteen minutes over path 21 totransfer the information provided by demand meter DM and accumulated indemand counter 26 to the comparator and storage circuit 29 and a briefinterval thereafter a clear pulse over path 22 to circuit 26. Inaddition, the demand clock generator 20 provides pulses alternately overpaths 23, 24', at the end of each 30.4 day period to transfer theinformation from at the 375/116 Hz rate. Such pulse is fed to the inputofa divider chain 248 which is comprised of three 16 dividers 250, 252and 254i respectively. The resultant output of divider 254 is a l/900 Hzsignal (i.e., a signal which occurs once every fifteen minutes). Inaddition, a first count is taken from the D3, B3, A3, C2, A2, D1, C1, B1outputs of divider chain 248 to NAND gate 256 which thus decodes count2910 (i.e., when each input to NAND gate 256 is logic 1). As each countof 2910 pulses is effected, a logic 0 pulse to one shot multivibrator265 (which is the same circuit as 250-FIG. 2) results in a delay pulseover inverter 266. The delay pulse thus provided is fed over conductors267, 268 to (a) the resets for divider chain 248, and (b) path 21 to theenable input of the comparator and storage circuit 29 (FIG. 4) (i.e., a15 minute store pulse which enables the comparator and storage circuit29 to ascertain whether the latest 15 minute count accumulated isgreater than any other 15 minute count accumulated in the same 30.4 dayperiod). In addition, the output of inverter 266 is also fed to theinput of a further pulse generator 276 which responsively provides anoutput pulse (15 minute clear pulse) over path 22 which is approximatelyl,u.s to demand counter 26. Such pulse enables demand counter 26 toinitiate a new count of pulses output from demand meter DM for a further15 minute interval.

In addition, the pulse output of divider 248 at the end of each 15minute interval is fed to a 2922 divider chain 278 which comprises three16 dividers 280, 282, 284 series connected to provide an output overpath 285 once each 730.5 hours (which is approximately 30.4 days) to aflip-flop circuit 286. One output A of flip-flop 236 is connected viapulse generator 288 (the same circuit as generator 250-FIG. 2) to path23 and alternate monthly accumulator 34-. Assuming flipflop 286 changesstate at the end of a first 30.4 day period to provide a logic 1 outputat terminal A, a pulse is generated by pulse generator 288 and fed overalternate month storage conductor 23 to alternate month accumulator 38.

After the expiration of the next 30.4 day period, the change of state ofthe flip-flop 286 effected by divider 278 will provide a logic 1 and Aterminal and pulse generator 289 (which is the same circuit as pulsegenerator will provide a storage pulse over alternate month storeconductor 24 to the alternate month accumulator 3 1 (FIG. 4). I

The demand clock generator 20 also provides a monthly clear pulse overoutput conductor 25. The circuitry for generating such pulse includesNAND gate 290 which has its inputs connected to D6, B6, A6, C5, B5, D4,B4 of divider chain 278 whereby logic 1 appears at each input to NANDgate 290 whenever divider 278 advances to count 2922. At such time theoutput of gate 290 goes to logic 0 and pulse generator 292 (which is thesame circuit as pulse generator 150) provides an output pulse overinverter 294, which via path 296 effects clearing of the dividers 2E0,282, 284 in chain 278 to thereby initiate the measurement of a furtherperiod of 30.4 days.

The output pulse over conductor 205 is also fed over path 297 to afurther pulse generator 298 (same circuit as pulse generator 150) whichprovides a delayed pulse over conductor 25 as a monthly clear pulseto'comparator and storage circuit 29 (FIG. 4

Demand Counter 26 As described in the above identified copendingapplication Ser. No. 53,745, a switch of the type disclosed in theapplication to Dale F. Becker having Ser. No. 829,160 which was filedMay 26, 1969, may be used to provide a pulse output to indicate thenumber of revolutions of the demand meter disc.

As in the copending application, the switch is connected to provide achange of potential on each conductor of a pair (27a,27bFlG. 3) as eachunit is measured by the sensing device. Thus if there is no potential(logic 1) on both conductors 27a,27b or the potential on both conductorsis ground (logic there will be no change in the state of flip-flop 300which is connected to conductors 27a, 27b. However, whenever conductor27a is logic 1 and conductor 27b is logic 0, or conductor 27a is logic 0and conductor 27b is logic 1, the associated flip-flop 300 will providea pulse over the output 317 to the divider chain 325 which in theillustrated embodiment has the ability to count 4,096 pulses. Such chaincomprises two 16 dividers 326, 328 respectively connected in series,which accumulates the pulses input thereto from the demand meter DM viaflip-flop 300 during each fifteen minute interval.

With reference once more to conductors 27a, 27b which feed pulses fromthe demand meter sensor to the flip-flop circuit 300, it will be seenthat the input conductor 27a is connected over inverter 301 to one inputof NAND gate 308, and is also connected over path 302 to the first inputof NAND gate 306. The second input conductor 27b is connected overinverter 304 and path 305 to the second input of NAND gate 306 and alsoover path 307 to the second input of NAND gate 308. The output of NANDgate 306 is connected over path 309 to one input of NAND gate 310 andthe output of NAND gate 308 is connected over path 316 to one input ofNAND gate 312. The output of NAND gate 312 is connected to the secondinput of NAND gate 310 and the output of NAND gate 310 os connected overpath 317 to the first input of NAND gate 312 and also to the input fordivider chain 325.

As will be shown, a change in the output over conductor 317 to thecounter 325 occurs only when the signals on 27a,27b are of differentlogic, and the logic on both conductors has changed from a previouscondition. Thus, if the input on conductor 27a is a logic 1 and theinput on conductor 27b is logic 0, and conductor 27a changes to logic 0,there will be no change in the output on conductor 317. However, at suchtime as the output on conductor 27b changes to logic 1 and the output onconductor 27a is logic 0, an output pulse will appear on conductor 317.

Such mode of operation is basically the result of the output of NANDgate 310 holding the NAND gate 312 against change until both inputs 27a,27b have changed state to a logic signal different from that whichpreviously appeared thereon.

By way of example, if both 27a and 27b are logic l, gates 306, 308 eachhave one input at logic 0 and their outputs are logic l, and there willbe no change in the outputs of gates 310, 312. lfboth 27a and 27b werelogic 0, the same condition exists. If input 27a goes to logic 0 andinput 27b goes to logic I, gate 312 will not change state.

Summarily, a pulse will be output over conductor 317 to counter 325 onlyif the logic of the conductors 27a, 27b changes from a previous state,such state having been one in which the logic on the two conductors 27a,27b was different. It will be apparent that logic l, logic 0 signals maybe represented by potentials of two different levels or by signals oftwo different polarities if desired, in which case the circuitry 300would be correspondingly modified. Each such pulse is added to the countwhich is stored therein during measured 15 minute period.

The count on counter 325 which continually represents the energymeasured by the meter during each 15 minute period appears continuallyon the output conductors a-i of path 28 which conductors are connectedas inputs to a storage unit in the comparator and storage circuit 29(FIG. 4).

Comparator and Storage Circuit 29 It will be recalled that while thecount being accumulated during each 15 minute interval is always presenton conductors a-i ofpath 28 (FIG. 3), such count is not transferred tostorage until a storage pulse is received over conductor 21 from thedemand clock generator 20 (FIG. 3) at the end of each 15 minute period.

At such time the storage pulse as applied over path 21 is fed to oneinput of NAND gate 344 (FIG. 4) in the comparator and storage circuit29. As will now be shown, gate 344 will be enabled to effect storage ofthe count on path 28 only if such 15 minute count is larger than the ISminute count previously stored in storage circuit 340 during the current30.4 day period.

With reference to FIG. 4, it will be seen that comparator and storagecircuit 29 includes a storage circuit 340 comprising five flip-flops350, 360, 370, 380, 390. Each of the first four flip-flops, such as 350,has two inputs such as 351, 352 connected to a corresponding pair ofconductors a, b in path 28 output from the 15 minute counter 325. Thelast flip-flop 390 has a single input 391 connected to the ninthconductor i which is output from counter 325. Thus the count whichappears on the nine conductors output from counter 325 is continuallyapplied to the inputs of flip-flops 350-390.

For purposes of example, it will be assumed that as a result of aprevious 15 minute period a count of 122 was stored in storage circuit340, and that as the next 15 minute pulse is fed over path 21 tocomparator and storage circuit 29 the count on path 28 is 125 (i.e.,higher than the stored count).

The comparator and storage circuit 29 also includes a comparator stagewhich includes a first and second comparator 395, 394 (which may be ofthe type commercially available as SN74L85N), and a separator comparatorstage 396. Each comparator 395, 394 has two sections, each sectionhaving a set of inputs, such as A0, A1, B0, B1. Two outputs of eachflip-flop, such as 350, in the storage circuit 340 are connected tocontinually apply the signals representative of the last count storedthereon over two associated output conductors, such as 353, 354, toassociated ones of the inputs such as B0, B1, of its associatedcomparator circuits, such as 395. In addition the current count which iscontinually input over the associated two conductors of path 28 to eachflip-flop, such as 350, is also fed over conductors 351, 352 to inputsAl, A0 of the corresponding section of its comparator.

Thus, as will, be shown, the first section of comparator 395 willcontinually compare the count previously stored on flip-flop 350 withthe count presently input over conductors 351, 352 from demand counter26. ln like manner the second section of comparator 395 continuallycompares the count stored in flip-flop 360 with the count currentlyinput over conductors 361, 362 from demand counter 26.

By way of specific example, if the count stored on flip-flops 350, 360is 5, the B0, B1, B2, B3 inputs to the comparator 395 will be so marked(0101). Assuming the count on the counter 325 is 6 conductors 351, 352,361, 362 input to the A0, A1, A2, A3 inputs will be 01 10. Since thecount on the A inputs is larger than the count on the B input, thecomparator 395 will provide a logic I over conductor 393 to thecomparator 394. Briefly stated, a logic 1 signal will be provided by thecomparator 395 only if the current count on conductors 351, 352, 361,362 is the same as or larger than the count stored on the correspondingflip-flop 350, 360.

In a similar manner, if the count on the A0, A1, A2, A3 inputs ofcomparator 394 is the same as or larger than the count on the B0, B1,B2, B3 inputs, and a logic 1 occurs on input 393, a logic 1 signal willappear on output conductor 395'. Likewise if the input on conductor 391is the same as or larger than the output on conductor 393 and there is alogic 1 output on conductor 395 from comparator 394, comparator 396 inaccordance with known comparator techniques will cause a logic 1 toappear on conductor 404.

Summarily stated whenever the count input on path 28 is larger than thecount stored in storage circuit 340, a logic 1 pulse is provided by NANDgate 402 over path 404 as one input to gate 344. Accordingly, as the 15minute interval pulse is applied over path 21 to the first input of gate344, gate 344 will be enabled if, and only if, a logic 1 is applied toconductor 404 as a result of the count on path 28 being larger than thecount stored on storage circuit 340.

Assuming that the count input on path 28 is larger than stored count atthe time of the 15 minute pulse on conductor 21, gate 344 is enabled toprovide a logic pulse to inverter 346 which via conductor 347 provides alogic 1 pulse to the store inputs such as 355, 365, etc., for theflip-flops 350, 360, etc., to cause such flipflops to assume a statewhich represents the larger count which currently appears on path 28.

Such manner of comparison of the count stored on storage circuit 340with the count on path 28 every 15 minutes is continued for 730.5 hoursat which time a clear pulse is provided by demand clock generator 20over conductor 25 (as noted heretofore) t0 the reset terminal R for theflip-flop in storage circuit 340.

The value of the count stored in the storage circuit 340 continuallyappears over the nine output conductors of path 30 (which are the B0-B3,B0'B3' inputs and outputs of accumulators 394, 395 and the B0" output of396) and are fed over path 30 to the inputs for the 15 minute demandmultiplexer 32 (FIGSv 1 and 6). In addition, the same nine conductoroutput is fed over path 31 as inputs to the alternate month accumulators34 and 38 respectively (FIG.

Alternate Month Accumulators With reference to H6. 5, alternate monthaccumulator 34 is shown in detail and alternate month accumulator 38(which is an identical structure) is shown in block.

As noted above, the count stored on storage circuit 340 (and thereforethe output from the comparator and storage circuit 29 over path 31) willbe the highest 16 reading which occurred in any of the l5 minuteintervals in the 730.5 hour interval preceding the monthly transferpulse.

It will be further recalled that the transfer pulse which is provided bytime base generator 10 over conductor 23 to the accumulator 38 and thetransfer pulse which is provided over conductor 24 to accumulator 34occur at alternate 730.5 hour intervals. Assuming that both accumulators34, 38 are empty at the end of the first 730.5 hour period, the transferpulse over conductor 24 will cause the highest demand value which hasbeen accumulated in any 15 minute interval of the first 730.5 hours (andwhich is stored in the storage circuit 340) to be transferred over path31 to the alternate month accumulator 34.

As shown in FIG. 5 each accumulator comprises a full adder circuit whichincludes three adder circuits 410, 420, 430, (each of which may be ofthe type SN74L83N which are currently marketed by Texas Instruments). Itwill be apparent that the count which appears on input path 31 (andwhich is always the maximum count stored by storage circuit 340) iscontinually extended by each adder, such as 410, over its outputconductors, such as 441, 442, 451, 452, to a pair of associatedflip-flop storage circuits, such as 440, 450, in storage circuit 500.Thus the two bit input on conductor B0, B1 to the first adder 410 willbe extended over conductors 441, 442 to the flip-flop 440, and thetwobit input over conductors B2, B3 to adder 410 will be extended overconductor 451 and 452 to the input of a second associated flip-flop 450.Adders 420, 430 are connected in like manner to flip-flops 460, 470 and480, 490 respectively of storage circuit 500. Storage pulse conductor 23(which receives a store pulse every 1461 hours) is fed to the set inputsof each of the flipflops in storage circuit 500.

Assuming for exemplary purposes that a count of was stored in storagecircuit 500 as the result of a previous readout, such count will beapplied over conductor 445, 446, 455, 456, etc., to the second input setof each of the adders 410, 420, 430. Assuming further that the countinput over path 31 to accumulator 34 is 120 at the time of receipt ofthe transfer storage pulse on conductor 23, the count 120 input onconductor 31 is added with the count of 120 which appears on conductors445, 446, etc., and the count of 240 appears on conductors 441, 442491,492 for the flip-flop 440 490 in storage circuit 500 as the transferor storage pulse is applied to the flip-flops 440 490 in storage circuit500.

Summarily, as a store pulse is received over path 23 at the end of each2 month interval, the count which appears on the input path 31 to theaccumulator 34 is added to the count which has been previously stored instorage circuit 500, and the resultant total is stored in storagecircuit 500 as the storage pulse occurs.

it will be further seen that at the end of the first month, accumulator34 will store the maximum 15 minute count for such month in itsassociated storage circuit 500. Likewise at the end of the second periodof 730.5 hours, the transfer pulse on conductor 24 will cause the counton path 31 (which represents the highest demand reading for the secondmonth period) to be stored in accumulator 38. As the store pulse isreceived over input path 23 at the end of the third period of 730.4hours, the count stored on storage circuit 500 will be added to thecount input over path 311 and stored in storage circuit 500. In asimilar manner, the

count on path 31 at the end of the fourth such monthly interval will beadded to the previous count in accumulator 38 and stored in thecorresponding circuits therein.

The counts stored in accumulator 34 are continually fed over 12conductor path 35 to demand multiplexer 32 (FIGS. 1 and 6) and the countstored in accumulator 38 is continually fed over path 39 to multiplexer36 (FIGS. 1 and 6). With reference to FIG. 1, it will be seen from theforegoing description that the system continually provides a first countB which is output from comparator and storage circuit 29 over path 30 toa 15 minute demand multiplexer 32, a second count C which is output fromthe first alternate month accumulator 34 over path 35 to an alternatemonth multiplexer 36, and a count D which is input from the secondalternate month accumulator 38.

As has been explained earlier, if neither count C nor D provided byaccumulator 34, 38 has changed since the previous interrogation, count Bfrom the comparator and storage circuit 29 will be the demand reading.It can be shown that this condition will only occur somewhere betweenzero and 30.4 elapsed days.

If only count C or count D provided by accumulator 34 or 38 respectivelyhas changed, the amount of such change should be used as the demandreading. It can be shown that this condition will only occur somewherebetween zero and 60.9 days.

In the event that the outputs of both accumulators 34, 38 have changed,and less than 60.9 days have elapsed, the larger change is used as thedemand reading. In the unlikely event that more than 60.9 days haveelapsed, the outputs from accumulators 34 and 38 may havechanged twice,and demand can be estimated by using the smaller change or half thelarger change,

whichever is greater.

Multiplexing Information to Output Circuit The multiplexers 52, 32, 36,40 (FIG. 6) (which may be SN74I50N chips currently available from TexasInstruments) are operative in the manner set forth above to effect themultiplexing ofinformation over an associated OR gate 53 and path 54 tothe transponder unit 58 for readout by associated remote readingequipment.

Assuming the start of a new word generation cycle, time base generator10 (FIG. I) initially provides logic 1 inputs to C, 8, in path 17 whichvia gate 48 enables the strobe input of multiplexer 52. As the l-of-16signals (0000,0001, etc.,) provided by time base generator 16 are fedover path 15, multiplexer 52 is enabled in known manner to connect thelogic signals which are hardwired to inputs E-E13 serially out over path44 as the first fourteen data bits of the word being generated, andthereafter the logic signals which appear on inputs E14 and E15 to befed out over path 44. As explained above, the signals on path 16comprise the lout-of-4" selection signals (00, 1O, 01, ll) from timebase generator which identify the source of the information which isbeing included in the word (i.e., multiplexer 32, 36, 40, or 48).

Thus if when the signals on path 16 are 00, the th and 16th bits outputon path 44 will be 0, 0 respectively and as will be shown, theinformation from the next twelve bits will be obtained from multiplexer32. Select signal 10 on path 16 identifies multiplexer 36, signal 01 onpath 16 identifies multiplexer 40, and select signal I l on path 16identifies multiplexer 48.

With reference once more to the word generation, as the first 16 bitshave been provided by multiplexer 52 over conductor 44,the time basegenerator 10 provides an enable signal over conductor 18 to enable themeter reading multiplexer 50 (FIG. 7) to selectively transmit 12additional bits of information which are obtained from the one of themultiplexers 32, 36, 40 and 48 which has been identified by the selectsignal (logic I l is applied successively to conductors EM; Ln; IIM andLM) on path 16. With receipt of the enabling signals over path 18 (andlogic 1 on the E C inputs which define the data interval of each timeslot), gate 525 provides an enabling pulse during the data period ofeach time slot to gates 502, 51 0, 520, 530. At this time with signal 11on conductors L M in path 16, gate 502 is enabled to transmit the bitinformation which is continually provided by the fifteen minute demandmultiplexer 32 over path 33 to one input of gate 502.

The 12 serial bit signals output from gate 502 are fed over gate 504,inverter 508, path 51, OR gate 53 and path 54 and the input oftransponder 58 during the data intervals of time slots 16-28. As the12th time slot is completed, time base genrator 10 provides the startpulse over conductor 14 during the 29th time slot as described above. Itwill also be understood that the reference one signals are applied overconductor 13 during the sync interval of each time slot so that theinformation bits in the successive time slots are followed by areference one signal.

It will be recalled that the select signals on path 16 remain the samefor five readouts of the information on path 33. On the other hand theenabling signals over conductors 17 and 18 effect alternate enablementof multiplexers 52 and 50 as each successive word is generated. As aresult, the word described above is generated five times which includesthe count B output from multiplexer 32.

As the sixth word is generated, the enabling signal on path 16 changesto 01, (the identification code for count C output from monthlyaccumulator 34) and the signals on conductor I, M become 01 and gate 502is disabled.

As the time base generator 10 effects generation of the meter addressand the identification bits for the next multiplexer 34, and theenabling signal is provided over path 18 to gate 525 in multiplexer 50,gate 510 will be enabled (i.e., the conductors L M have logic 1, lthereon) and the bit information which is provided over path 37 to gate510 will be fed over gate 504, inverter 508, and OR gate 53 totransponder 58. Such cycle continues as before to effect transmission offive words including the information provided by multiplexer 36 totransponder 58.

In a similar manner, five successive words which include the datainformation provided by multiplexer 40 and five further words whichinclude the data information provided by multiplexer 48 are generatedand fed to transponder 58 by selective enablement of gates 520 and 530.I I

Transponder Transponder 58 may be of the type set forth in my copendingapplication which as shown in FIG. 7 comprises an antenna 530 having aseparate receive section 531 tuned to 915 MHz and having an impedancerepresented by lumped inductance L1 and a separate transmit section 532tuned to L830 MHz and having an impedance represented by lumpedinductance L2. The transmit section 532 and the receive section 531 areinterconnected by a semi-passive network 534 having a non-linearimpedance characteristic. The non-linear network 534 serves as theterminating impedance for the antenna 530 and basically comprise avariable capacitance diode 535. Such diode is a semi-conductor diodetype device, the junction capacitance of which varies inversely withreverse bias to provide a nonlinear loading for antenna 530 resulting indistortion of the 915 MHz interrogate signals received over receivesection 531 from the mobile van transmitter and thereby generatingharmonics of the signal received. The amount of reverse bias applied todiode 535 is varied in accordance with the value of the logic signalprovided over path 54 to transistor 540. Transistor 540 is connectedacross a B-lsource in series with resistor 54] and diode 544.

In operation as the mobile van unit transmits the 915 MHz signals in thedirection of the meter and such signals are received between the twosections 531, 532 of antenna 530 and impressed across reactor diode 535,the RF interrogate signals in swinging peak-to-peak through each cycleeffect a corresponding change in the impedance characteristic of diode535. As a result harmonics (including the second harmonic I830 MHz ofthe received signal) are generated.

The amplitudes of the harmonic signals thus generated are varied inaccordance with the bias level signals which are applied to the diode535 by transistor 540, which in turn is controlled to vary such bias bythe bits of the words being supplied over input path 54. Thus logic 1pulses will provide a signal level of approximately -1 with reverse biasacross diode 535, and the RF signals received at the 915 MHZ rate willbe distorted to provide second harmonic signals (1,830MI-Iz) at a levelof approximately 35db. Logic signals (which turn transistor 540 off)will cause a reverse bias of -12 volts to be applied to diode 535 andthereby prevent the generation of harmonics of the interrogate signal toindicate transmission of a logic 0 signal.

In an alternate embodiment transponder 58' may comprise an oscillatorcircuit 549 which is controlled to provide outputs in accordance withthe bits of the words input over path 54.

With reference to FIG. 9, it will be apparent that path 54 is connectedover resistance 539' to the base of transistor 540 which is connected asan oscillator 549 which oscillates at a MHZ frequency. The emitter oftransistor 540 is connected over diode 544 to ground and its collectoris connected to a tank circuit 554 which includes capacitor 547 andinductance 548 tuned to oscillate at a 10 megacycle frequency. The tankcircuit 554 in turn is connected to the base of a field transistor 550which has its output connected over coupling capacitor 552 to thereceiving section 53l of the antenna 530. Capacitors 55!, 553 areconnected as RF bypass condensers. The transmitting section of antenna530' is connected to voltage divider 542, 545' in the manner of theembodiment of PEG. '7.

In operation, as the mobile van approaches the unit, the interrogatingsignal of the mobile van is directly coupled to the receiving section53E of antenna 530. Oscillator 549 is turned on and off by logic 1,logic 0 bit outputs which are applied over path 5d to the base oftransistor 54f) (i.e., a logic 1 signal turns on the os- E li cillator5419 and a low level signal turns oscillator 549 off).

As noted in the above idsclosed embodiment, the output signal from themobile van is a 915 MHZ signal, As a logic 1 input on path 54 turns onthe oscillator 5419, the 10 MHZ output over field transistor 550 is fedacross diode 535. Since diode 535 is a non-linear device, the applied 10MHz signal is mixed with the 915 MHZ signal to provide a 915 MHz (P 10MHz (F,) or a 925 MHZ output, and a 915 MHZ (F 10 MHz (F or a 905 MHzoutput. Oscillator 549 turns diode 535 on and off at the 10 MHZ rateduring the period that a logic 1 bit is applied over path 54. During theperiod a logic 0 bit is applied over such path, the oscillator 549 isturned off, and diode 535 is off.

At the mobile van, the two input signals as received from the vehicleantenna (905 and 925 MHz) are mixed with the 915 MHz signal which wastransmitted (the same vehicle antenna being used for transmitting andreceiving). As a result of the strong F signal (915 MHz) at the mobilevan, the resultant output will comprise a weak F F (925 MHz) and a weakF F (905 MHZ) signal. The transmitted signal thus serves as.

a local oscillator and the difference frequency F is amplified, detectedand fed to a decoder generator for decoding and storage in theassociated storage equipment.

The advantage of such system is that three milliwatts of DC power asapplied to the oscillator 549 will result in at least 1 milliwatt outputto the diode 535' at the transponder 58. Such arrangement results inincreased range of signal reception. Further, since the frequencytransmitted is close to the frequency returned, there is less spaceloss. That is, space loss is a function of wave length, and at twice thefrequency, 6DB more path loss would occur.

In addition, since the output of the embodiment of FIG. 9 is a linearfunction of the input, an output signal of inward strength is availablewhich permits use of the system in weak signal areas.

By controlling the input to oscillator 549, the efficiency of theoscillator is changed and the maximum output of the return signal islimited. That is, it will always be less than the oscillator output.

Such arrangement simplifies the antenna at the transmitter (and alsosimplifies the receiver), since the local oscillator is built into thesystem. Operation of the system at a lower frequency also results inbetter signal to noise ratio.

We claim:

I. In a remote meter reading system having meters for measuring quantumsof a commodity, at least one meter including indicator means forproviding signals indicating the total quantum measurement by said onemeter for each predetermined interval of a given time period, means forproviding a measurement of the total quantum for each interval includingfirst means enabled thereby to store the measurement for an intervalwhenever such measurement is larger than the maximum measurement for anyprevious predetermined interval, accumulator means, means fortransferring the value of the stored measurement to said accumulatormeans at the end of a given time period and thereupon clearing thestored measurement from said first means, transponder means fortransmitting signals to a remote location, readout means including firstmeans for selectively providing signals representing the value of themeasurement stored in said storage means to said transponder means, andsecond means for selectively providing signals which represent themeasurements which are stored in said accumulator means to saidtransponder means.

2. In a remote meter reading system having meters for measuring quantumsof a commodity, at least one meter having means for providing signalsindicating the total quantum measurement for each predetermined intervalof a given time period, comparison means for comparing the measurementfor each interval with the previous maximum measurement in said giventime period including storage means for storing the value of the largestmeasurement of each such comparison, accumulator means, means fortransferring the value of the measurement in said storage means to saidaccumulator means at the end ofa given time period and thereuponclearing such measurement from said storage means, transponder means fortransmitting signals to a remote location, and readout means includingfirst means for selectively providing signals representing the value ofthe stored measurement in said storage means to said transponder means,and second means for selectively providing signals which represent themeasurements which are stored in said accumulator means to saidtransponder means.

3. A system as set forth in claim 2 which includes means for enablingsaid comparison by said comparison means at the end of eachpredetermined interval of minutes, and in which said means whichtransfer the value of the measurement in said storage means to saidaccumulator means are enabled at the end of each given time period ofapproximately 30.4 days.

4. A system as set forth in claim 2 in which said readout means includescontrol means for enabling said first and second means to sequentiallyprovide the signals to said transponder means which represent themeasurements stored in said storage means and said accumulator means. 5.A system as set forth in claim 4 which includes meter address means forproviding meter identification signals, and in which said control meansare operative to enable said meter address means to provide said meteraddress to said transponder means along with said measurements providedby said storage means and said accumulator means.

6. A system as set forth in claim 2 which said accumulator meansincludes first accumulator means for storing the value of the largestmeasurement stored in said storage means at the end of a first measuredtime period, second accumulator means for storing the largestmeasurement stored in said storage means at the end of a secondvmeasured time period.

7. A system as set forth in claim 6 in which said first and secondaccumulator means each includes means for providing a cumulative totalof the measurements provided thereto by said storage means duringalternate ones of successive time periods, and the measurement providedto said transponder means by said further means are said cumulativetotals.

8. A system as set forth in claim 2 in which said measurements arestored in said storage means and said accumulator means as logic bits,and in which said readout means includes multiplexer means for effectingreadout of said logic bits in word form,and means for providing logicbits in each word which represents the meter address.

9. A system as set forth in claim 4 in which said first and second meanscomprise a first, second and third multiplexer which are simultaneouslysampled in a cyclic manner, and in which said readout means includes afurther multiplexer for selectively forwarding the output of said first,second and third multiplexers in a predetermined sequence.

10. A system as set forth in claim 9 which includes means for providingsignals which represent the total measurement made by said meter at anygiven time, and in which said further multiplexer selectively ex tendssaid output to said transponder with the outputs of said first, secondand third multiplexer.

11. A system as set forth in claim 1 which includes separate countermeans for providing a cumulative count of the total number of signalsprovided by said indicator means.

12. In a remote meter reading system having meters for measuring thequantum of a commodity as used, at least one meter including indicatormeans for providing an input signal which indicates a given measurementby said meter, demand counter means connected to count the input signalsfor each predetermined interval of a given time period, storage means,comparator circuit means having first input means connected to theoutput of said demand counter means and second input means connected tothe output of said storage means, means connecting the input of saidstorage means to the output of said demand counter means, and enablingmeans for enabling said comparator means at the end of each of saidintervals to compare the count stored in said storage means with thecount provided by said demand counter means, means controlled by saidcomparator means for enabling said storage means to store the largest ofthe two counts in each comparison, accumulator means, and means foreffecting transfer of the count stored in said storage means to saidaccumulator means, said accumulator means including an adder circuithaving its input connected to the output of said storage means, afurther storage means having its input connected to the output of saidadder circuit, and means connecting the output of said further storagemeans to the input of said adder circuit, whereby each new count inputto said adder circuit from said storage means is added to the previoustotal count in said further storage means and the total thereof is fedto said further storage means.

13. A system as set forth in claim 12 which includes a multiplexercircuit connected to the output of said further storage means in saidaccumulator means, and means for periodically enabling said multiplexerto provide a readout of the accumulated counts stored in the furtherstorage means of said accumulator means.

14. In a remote meter reading system-having meters for measuring thequantum of a commodity as used, at least one meter including indicatormeans for providing an input signal which indicates a given measurementby said meter, demand counter means connected to count the input signalsfor each predetermined interval of a given time period, storage means,comparator circuit means having first input means connected to theoutput of said demand counter means and second input means connected tothe output of said storage means, means connecting the input of saidstorage means to the output of said demand counter means, and enablingmeans for enabling said comparator means at the end of each of saidintervals to compare the count stored in said storage means with thecount provided by said demand counter means, means controlled by saidcomparator means for enabling said storage means to store the largest ofthe two counts in each comparison, a first accumulator, means forenabling said first accumulator to store the count in said storage meansafter certain ones of said time periods, a second accumulator, means forenabling the second accumulator to store the counts in said storagemeans at the end of alternate ones of said time periods, a plurality ofmultiplexer circuits for effecting readout of the counts in said storagemeans and said first and second accumulators, and selection means forenabling said multiplexer circuits in sequence to provide sequentialreadout of the counts stored in said storage means and said first andsecond accumulator means.

15. A system as set forth in claim 14 in which said selection meansincludes means for providing coded signals to enable said multiplexercircuit, different coded signals being provided to enable acorrespondingly different one of said multiplexer circuits, and whichincludes further means controlled by said coded signals to provideidentification signals for the one of said multiplexer circuits which isproviding the count.

16. A system as set forth in claim 15 in which said further meansincludes meter address means for providing a meter identificationaddress for the meter along with the information and identificationsignals provided for said multiplexer circuit.

17. In a remote meter reading system having station means forselectively requesting meter information from a meter at a remotelocation, at least one demand meter in said system which includes meansfor providing signals indicating the maximum reading for each intervalof a given time period, means including comparator means for comparingthe reading for each interval with the maximum reading previouslydetected in said given time period, and storage means for storing thevalue of the largest of the two readings, transponder means, means fortransmitting signals representing the maximum reading stored in saidstorage means to said transponder means, antenna means for saidtransponder means operative to receive input signals of a firstfrequency from said station means, nonlinear impedance means connectedto said antenna means operative to distort said input signals togenerate related harmonic signals, and means for modulating saidharmonic signals with said stored signals prior to transmission oversaid antenna means to said station means.

18. A system as set forth in claim ll7 in which said stored signals arestored as first and second signal bits, and in which said means formodulating said harmonic signals includes an oscillator circuit biassedto be turned on and off by said first and second signal bitsrespectively, and means coupling the output of said oscillator circuitacross said nonlinear impedance means.

i9. In a remote meter reading system having station means forselectively requesting meter information from a meter at a remotelocation, at least one meter in said system which includes means forproviding signals indicating the reading on said meter, and storagemeans for storing said reading, transponder means, means fortransmitting signal bits of different types to represent said readingstored in said storage means to said transponder means, antenna meansfor said transponder means operative to receive input signals of a firstfrequency from said station means, nonlinear impedance means connectedto said antenna means operative to distort said input signals togenerate related harmonic signals, and means for modulating saidharmonic signals with said stored signals prior to transmission oversaid antenna means to said station means, including an oscillatorcircuit turned on and off by different ones of said stored signal bits,and means coupling the output of said oscillator circuit across saidnonlinear impedance means.

20. A method of remotely reading meters in a multimeter system whichcomprises the steps of providing signals which indicate the value of themaximum measurement made in each interval of a given time period,storing the maximum reading obtained in the first interval of said timeperiod in associated storage means, comparing the maximum readingobtained in the next interval with the maximum reading stored in thefirst interval of said given time period, and storing in said storagemeans the largest reading of the two compared readings, comparing themaximum readings obtained in each further interval of said given timeperiod with the maximum one of the readings previously stored in thestorage means, and in each case storing the largest reading of the tworeadings thus compared, transferring the maximum reading in said storagemeans at the end of said given time period to an accumulator, andselectively providing the maximum reading in said storage means and themaximum reading in said accumulator for use in a demand readingcalculation.

21. A method of remotely reading meters in a multimeter system whichcomprises the steps of providing a pulse count indicating the value ofthe maximum measurement made in each interval ofa given time period,storing the maximum count obtained in the first interval of said timeperiod in associated storage means, comparing the maximum count obtainedin the next interval with the maximum stored count obtained in the firstinterval of said given time period, storing in said storage means thelargest count of the two compared counts, comparing the maximum countsobtained in each further interval of said given time period with themaximum one of the counts previously stored in said storage means, andin each case storing the largest count of the two counts thus compared,transferring the maximum count in said storage means at the end of saidgiven time period to a first accumulator, transferring the maximum countin said storage means at the end of a second time period to a secondaccumulator, and selectively providing the maximum count in said storagemeans and the maximum counts in said first and second accumulators foruse in a demand reading calculation.

22. A method of remotely reading meters in a multimeter system whichcomprises the steps of determining the value of the maximum measurementmade in each one of a plurality of intervals of a given time period,storing said maximum measurement from a first one of said time periodsin a first accumulator, storing the maximum measurement for a second oneof said time periods in a second accumulator, and continually providingthe largest measurement made in progressive intervals of a third one ofsaid time periods, comparing the output of said storage means in saidfirst and second accumulators with the output at the time of a previous

1. In a remote meter reading system having meters for measuring quantumsof a commodity, at least one meter including indicator means forproviding signals indicating the total quantum measurement by said onemeter for each predetermined interval of a given time period, means forproviding a measurement of the total quantum for each interval includingfirst means enabled thereby to store the measurement for an intervalwhenever such measurement is larger than the maximum measurement for anyprevious predetermined interval, accumulator means, means fortransferring the value of the stored measurement to said accumulatormeans at the end of a given time period and thereupon clearing thestored measurement from said first means, transponder means fortransmitting signals to a remote location, readout means including firstmeans for selectively providing signals representing the value of themeasurement stored in said storage means to said transponder means, andsecond means for selectively providing signals which represent themeasurements which are stored in said accumulator means to saidtransponder means.
 2. In a remote meter reading system having meters formeasuring quantums of a commodity, at least one meter having means forproviding signals indicating the total quantum measurement for eachpredetermined interval of a given time period, comparison means forcomparing the measurement for each interval with the previous maximummeasurement in said given time period including storage means forstoring the value of the largest measurement of each such compaRison,accumulator means, means for transferring the value of the measurementin said storage means to said accumulator means at the end of a giventime period and thereupon clearing such measurement from said storagemeans, transponder means for transmitting signals to a remote location,and readout means including first means for selectively providingsignals representing the value of the stored measurement in said storagemeans to said transponder means, and second means for selectivelyproviding signals which represent the measurements which are stored insaid accumulator means to said transponder means.
 3. A system as setforth in claim 2 which includes means for enabling said comparison bysaid comparison means at the end of each predetermined interval of 15minutes, and in which said means which transfer the value of themeasurement in said storage means to said accumulator means are enabledat the end of each given time period of approximately 30.4 days.
 4. Asystem as set forth in claim 2 in which said readout means includescontrol means for enabling said first and second means to sequentiallyprovide the signals to said transponder means which represent themeasurements stored in said storage means and said accumulator means. 5.A system as set forth in claim 4 which includes meter address means forproviding meter identification signals, and in which said control meansare operative to enable said meter address means to provide said meteraddress to said transponder means along with said measurements providedby said storage means and said accumulator means.
 6. A system as setforth in claim 2 which said accumulator means includes first accumulatormeans for storing the value of the largest measurement stored in saidstorage means at the end of a first measured time period, secondaccumulator means for storing the largest measurement stored in saidstorage means at the end of a second measured time period.
 7. A systemas set forth in claim 6 in which said first and second accumulator meanseach includes means for providing a cumulative total of the measurementsprovided thereto by said storage means during alternate ones ofsuccessive time periods, and the measurement provided to saidtransponder means by said further means are said cumulative totals.
 8. Asystem as set forth in claim 2 in which said measurements are stored insaid storage means and said accumulator means as logic bits, and inwhich said readout means includes multiplexer means for effectingreadout of said logic bits in word form,and means for providing logicbits in each word which represents the meter address.
 9. A system as setforth in claim 4 in which said first and second means comprise a first,second and third multiplexer which are simultaneously sampled in acyclic manner, and in which said readout means includes a furthermultiplexer for selectively forwarding the output of said first, secondand third multiplexers in a predetermined sequence.
 10. A system as setforth in claim 9 which includes means for providing signals whichrepresent the total measurement made by said meter at any given time,and in which said further multiplexer selectively extends said output tosaid transponder with the outputs of said first, second and thirdmultiplexer.
 11. A system as set forth in claim 1 which includesseparate counter means for providing a cumulative count of the totalnumber of signals provided by said indicator means.
 12. In a remotemeter reading system having meters for measuring the quantum of acommodity as used, at least one meter including indicator means forproviding an input signal which indicates a given measurement by saidmeter, demand counter means connected to count the input signals foreach predetermined interval of a given time period, storage means,comparator circuit means having first input means connected to theoutput of said demand counter means and second input means connected tothe output of said storage means, meaNs connecting the input of saidstorage means to the output of said demand counter means, and enablingmeans for enabling said comparator means at the end of each of saidintervals to compare the count stored in said storage means with thecount provided by said demand counter means, means controlled by saidcomparator means for enabling said storage means to store the largest ofthe two counts in each comparison, accumulator means, and means foreffecting transfer of the count stored in said storage means to saidaccumulator means, said accumulator means including an adder circuithaving its input connected to the output of said storage means, afurther storage means having its input connected to the output of saidadder circuit, and means connecting the output of said further storagemeans to the input of said adder circuit, whereby each new count inputto said adder circuit from said storage means is added to the previoustotal count in said further storage means and the total thereof is fedto said further storage means.
 13. A system as set forth in claim 12which includes a multiplexer circuit connected to the output of saidfurther storage means in said accumulator means, and means forperiodically enabling said multiplexer to provide a readout of theaccumulated counts stored in the further storage means of saidaccumulator means.
 14. In a remote meter reading system having metersfor measuring the quantum of a commodity as used, at least one meterincluding indicator means for providing an input signal which indicatesa given measurement by said meter, demand counter means connected tocount the input signals for each predetermined interval of a given timeperiod, storage means, comparator circuit means having first input meansconnected to the output of said demand counter means and second inputmeans connected to the output of said storage means, means connectingthe input of said storage means to the output of said demand countermeans, and enabling means for enabling said comparator means at the endof each of said intervals to compare the count stored in said storagemeans with the count provided by said demand counter means, meanscontrolled by said comparator means for enabling said storage means tostore the largest of the two counts in each comparison, a firstaccumulator, means for enabling said first accumulator to store thecount in said storage means after certain ones of said time periods, asecond accumulator, means for enabling the second accumulator to storethe counts in said storage means at the end of alternate ones of saidtime periods, a plurality of multiplexer circuits for effecting readoutof the counts in said storage means and said first and secondaccumulators, and selection means for enabling said multiplexer circuitsin sequence to provide sequential readout of the counts stored in saidstorage means and said first and second accumulator means.
 15. A systemas set forth in claim 14 in which said selection means includes meansfor providing coded signals to enable said multiplexer circuit,different coded signals being provided to enable a correspondinglydifferent one of said multiplexer circuits, and which includes furthermeans controlled by said coded signals to provide identification signalsfor the one of said multiplexer circuits which is providing the count.16. A system as set forth in claim 15 in which said further meansincludes meter address means for providing a meter identificationaddress for the meter along with the information and identificationsignals provided for said multiplexer circuit.
 17. In a remote meterreading system having station means for selectively requesting meterinformation from a meter at a remote location, at least one demand meterin said system which includes means for providing signals indicating themaximum reading for each interval of a given time period, meansincluding comparator means for comparing the reading for each intervalwith the maximum reading previously detected in said given time period,and storage means for storing the value of the largest of the tworeadings, transponder means, means for transmitting signals representingthe maximum reading stored in said storage means to said transpondermeans, antenna means for said transponder means operative to receiveinput signals of a first frequency from said station means, nonlinearimpedance means connected to said antenna means operative to distortsaid input signals to generate related harmonic signals, and means formodulating said harmonic signals with said stored signals prior totransmission over said antenna means to said station means.
 18. A systemas set forth in claim 17 in which said stored signals are stored asfirst and second signal bits, and in which said means for modulatingsaid harmonic signals includes an oscillator circuit biassed to beturned on and off by said first and second signal bits respectively, andmeans coupling the output of said oscillator circuit across saidnonlinear impedance means.
 19. In a remote meter reading system havingstation means for selectively requesting meter information from a meterat a remote location, at least one meter in said system which includesmeans for providing signals indicating the reading on said meter, andstorage means for storing said reading, transponder means, means fortransmitting signal bits of different types to represent said readingstored in said storage means to said transponder means, antenna meansfor said transponder means operative to receive input signals of a firstfrequency from said station means, nonlinear impedance means connectedto said antenna means operative to distort said input signals togenerate related harmonic signals, and means for modulating saidharmonic signals with said stored signals prior to transmission oversaid antenna means to said station means, including an oscillatorcircuit turned on and off by different ones of said stored signal bits,and means coupling the output of said oscillator circuit across saidnonlinear impedance means.
 20. A method of remotely reading meters in amultimeter system which comprises the steps of providing signals whichindicate the value of the maximum measurement made in each interval of agiven time period, storing the maximum reading obtained in the firstinterval of said time period in associated storage means, comparing themaximum reading obtained in the next interval with the maximum readingstored in the first interval of said given time period, and storing insaid storage means the largest reading of the two compared readings,comparing the maximum readings obtained in each further interval of saidgiven time period with the maximum one of the readings previously storedin the storage means, and in each case storing the largest reading ofthe two readings thus compared, transferring the maximum reading in saidstorage means at the end of said given time period to an accumulator,and selectively providing the maximum reading in said storage means andthe maximum reading in said accumulator for use in a demand readingcalculation.
 21. A method of remotely reading meters in a multimetersystem which comprises the steps of providing a pulse count indicatingthe value of the maximum measurement made in each interval of a giventime period, storing the maximum count obtained in the first interval ofsaid time period in associated storage means, comparing the maximumcount obtained in the next interval with the maximum stored countobtained in the first interval of said given time period, storing insaid storage means the largest count of the two compared counts,comparing the maximum counts obtained in each further interval of saidgiven time period with the maximum one of the counts previously storedin said storage means, and in each case storing the largest count of thetwo counts thus compared, transferring the maximum count in said storagemeans at the end of said given time period to a first accumulator,transferring the maximum count in said storage means at the end of asecond time period to a second accumulator, and selectively providingthe maximum count in said storage means and the maximum counts in saidfirst and second accumulators for use in a demand reading calculation.22. A method of remotely reading meters in a multimeter system whichcomprises the steps of determining the value of the maximum measurementmade in each one of a plurality of intervals of a given time period,storing said maximum measurement from a first one of said time periodsin a first accumulator, storing the maximum measurement for a second oneof said time periods in a second accumulator, and continually providingthe largest measurement made in progressive intervals of a third one ofsaid time periods, comparing the output of said storage means in saidfirst and second accumulators with the output at the time of a previousreading and using the reading in said storage means for the billed meterreading whenever the measurement in the first and second accumulator isunchanged from the previous reading.
 23. The method of claim 22 whichincludes the further step whenever one of the accumulators has a readingdifferent than its previous reading of providing the reading of the oneof said accumulators which has changed.
 24. The method of claim 22 whichincludes the further step whenever the reading on the first and secondaccumulator has changed, of providing the change in reading on the oneof the accumulators which shows the largest change.